I Can’t Sleep - Light | Gentle Reading to Help You Fall Asleep

Episode Date: February 18, 2020

Unwind with calm bedtime reading about light to help ease insomnia and restless nights. This soothing episode explores the nature and science of light while creating a peaceful space for sleep. Benjamin’s gentle cadence makes complex ideas—from photons and wavelengths to the speed of light—easy to absorb without effort. There’s no whispering or hypnosis, just relaxing education to calm your mind, reduce stress, and settle anxiety. Press play, learn something new, and drift into rest. Want More? Request a Topic: https://www.icantsleeppodcast.com/request-a-topic Ad-Free Episodes: https://icantsleep.supportingcast.fm/ Shop Sleep-Friendly Products: https://www.icantsleeppodcast.com/sponsors Join the Discussion on Discord: https://discord.gg/myhGhVUhn7 This content is derived from the Wikipedia article on Light, available under the Creative Commons Attribution-ShareAlike (CC BY-SA) license. Read the full article: Wikipedia – Light. Happy sleeping! Learn more about your ad choices. Visit megaphone.fm/adchoices

You're listening to a Glassbox media podcast. What if I told you that most of the modern day self-help advice you've been hearing could actually make you worse? The key to a better life isn't about feel-good gimmicks that sound catchy. The Mentally Stronger Podcast gives you access to a licensed therapist who shares science-backed tools that will actually change your life. Hi, I'm Amy Morin, psychotherapist, mental strength trainer, and international best-selling author. In each episode, we cover research-back strategies, like how to stop relying on willpower and start creating habits for lasting change. And the five mental strength-building exercises you can do from your couch.

I also speak to world-class experts like Dr. Nicole Kane, who shares how to permanently heal anxiety by addressing the root cause. With over 200 episodes in our catalog, this podcast is for you if you're ready to crush self-doubt, conquer challenges, and become stronger than ever with therapist-approved strategies that can change your life. Listen to Mentally Stronger with Therapist Amy Morin, wherever you get your podcasts. Welcome to the I Can't Sleep podcast, where I read random articles from across the web to bore you to sleep with my soothing voice. I'm your host, Benjamin Boster. Today's episode is from a Wikipedia article titled, Light, Light or Ville.

Visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400 to 700 nanometers, or 4 times 10 to the negative 7 to 7 to the negative 7 meters, between the infrared with longer wavelengths and the ultraviolet with shorter wavelengths. This wavelength means a frequency range of roughly 430 to 750 terahertz. The main source of light on Earth is the sun. Sunlight provides the energy that green plants use to create sugars, mostly in the form of starches, which releases energy into the living things that digest them.

This process of photosynthesis provides virtually all the energy used by living things, Historically, another important source of light for humans has been fire, from ancient campfires to modern kerosene lamps. With the development of electric lights and power systems, electric lighting has effectively replaced firelight. Some species of animals generate their own light, a process called bioluminescence. For example, fireflies use light to locate maids, and vampire squids use it to hide themselves. from prey. The primary properties of visible light are intensity, propagation, direction,

frequency, or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,000, 458 meters per second, is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation, EMR, is experimentally found to always move at this speed in a vacuum. In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, x-rays, microwaves, microwaves, and radio waves are also light. Like all types of EM radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed.

The absorbed energy of the EM waves is called a photon and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location, and this location is where the photon arrives. This is what is called the wave function collapse, this dual wave-like and particle-like nature, of light is known as the wave particle duality. A study of light known as optics is an important

research area in modern physics. Electromagnetic spectrum and visible light. Generally, EM radiation, the designation radiation excludes static electric, magnetic, and near fields, or EMR, is

classified by wavelength into radio waves, microwaves, infrared, the visible spectrum, that we perceive as light, ultraviolet, x-rays, and gamma rays. The behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. When EMR interacts with single atoms and molecules, its behavior depends on the amount of energy per quantum it carries. EMR in the visible light region consists of quanta, called photons,

that are at the lower end of the energies that are capable of causing electronic excitation within molecules. EMR in the visible light region consists of quanta, called photons, that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which leads to changes in the bonding or chemistry of the molecule. At the lower end of the visible light spectrum, EMR becomes invisible to humans, infrared, because its photons no longer have enough individual energy

to cause a lasting molecular change, a change in confirmation, and the visual molecule retinal in the human retina, which change triggers the sensation of vision. There exist animals that are sensitive to various types of infrared, but not by means of quantum absorption. Infrared sensing and snakes depends on a kind of natural thermal imaging, in which tiny packets of cellular water are raised in temperature by the infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detected. Above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nanometers

and the internal lens below 400 nanometers. Furthermore, the rods and cones located in the retina of the human eye cannot detect the very short below 360 nanometers ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses, such as insects and shrimp, are able to detect ultraviolet by quantum photon absorption mechanisms in much the same chemical way that humans detect visible life.

Various sources define visible light as narrowly as 420 to 680 nanometers to as broadly as 360 to 800 nanometers. Under ideal laboratory conditions, people can see infrared up to at least 1,050 nanometers. Children and young adults may perceive, ultraviolet wavelengths down to about 310 to 313 nanometers. Plant growth is also affected by the color spectrum of light, a process known as photomorphogenesis. Speed of light The speed of light in a vacuum is defined to be exactly 299,792,458 meters per second.

The fixed value of the speed of light in SI units results from the fact that the meter is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed and vacuum. Different physicists have attempted to measure the speed of light throughout history. Galileo attempted to measure the speed of light in the 17th century. An early experiment to measure the speed of light was conducted by Ola Ruma, a Danish physicist in 1676. Using a telescope, Rumor observed the motions of Jupiter and one of its moons, Io. Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about

22 minutes to traverse the diameter of Earth's orbit. However, its size was not known at that time. If Rumor had known the diameter of the Earth's orbit, he would have calculated a speed of 227 million meters per second. Another more accurate measurement of the speed of light was performed in Europe by Hippolyt Vizzo in 1849. Fizo directed a beam of light at a mirror several kilometers away. A rotating cogwheel was placed in the path of the light beam as it traveled from the source to the mirror and then returned to its origin.

Fizzo found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Vizzo was able to calculate the speed of light as 313 million meters per second. Leon Foucault carried an experiment which used rotating mirrors to obtain a value of 298 million meters per second in 1862. Albert A. Meckleson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926, using improved rotating mirrors

to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California. The precise measurements yielded to speed of 299,796,000 meters per second. The effect of velocity of light in various transparent substances containing ordinary matter is less than in vacuum. For example, the speed of light and water is about three-fourths of that in vacuum. Two independent teams of physicists were said to bring light to a complete standstill by passing it through a Bose-Einstein condensate of the element rubidium, one team at Harvard University and the Roland Institute of Science in Cambridge, Massachusetts. and the other at the Harvard-Smithsonian Center for Astrophysics, also in Cambridge. However, the popular description of light being stopped in these experiments

refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time as stimulated by a second laser pulse. During the time it had stopped, it had ceased to be light. Optics The study of light and the interaction of light and matter is termed optics. The observation and study of optical phenomena such as rainbows and the aurora borealis

offer many clues as to the nature of light. Refraction Refraction is a bending of light rays when passing through a surface between one transparent material and another. It is described by Snell's law. When a beam of light crosses the boundary between a vacuum and another medium

or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal, or rather normal, to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction. The refractive quality of lenses is frequently used to manipulate light in order to change the apparent size of images. Magnifying glasses, spectacles, contact lenses,

microscopes, and refracting telescopes are all examples of this manipulation. Light sources There are many sources of light. A body at a given temperature emits a characteristic spectrum of black body radiation. A simple thermal source is sunlight, the radiation emitted by the chromosphere of the sun at around 6,000 Kelvin's, peaks in the visible region of the electromagnetic spectrum when plotted in wavelength units. and roughly 44% of sunlight energy that reaches the ground is visible.

Another example is incandescent light bulbs, which emit only around 10% of their energy is visible light, and the remainder is infrared. A common thermal light source in history is the glowing solid particles and flames, but these also emit most of their radiation in the infrared, and only a fraction in the visible spectrum. The peak of the black body spectrum is in the deep infrared at about 10 micrometer wavelength for relatively cool objects like human beings.

As the temperature increases, the peak shifts to shorter wavelengths, producing first a red glow than a white one, and finally a blue white color as the peak moves out of the visible part of the spectrum and into ultraviolet. These colors can be seen when metal is heated to red-hot, or white-hot. Blue-white thermal emission is not often seen except in stars. The commonly seen pure blue color in a gas flame or a welder's torch is in fact due to

molecular emission, notably by CH radicals, emitting a wavelength band around 425 nanometers, and is not seen in stars or pure thermal radiation. atoms emit and absorb light at characteristic energies. This produces emission lines. in the spectrum of each atom. Emission can be spontaneous, as in light-emitting diodes, gas-charged lamps, such as neon lamps and neon signs, mercury-vapar lamps, etc.,

and flames, light from the hot gas itself, so, for example, sodium in a gas flame, emits characteristic yellow light. Emission can also be stimulated, as in a laser or a microwave mazer. Deceleration of a free-charged particle, such as an electron, can produce visible radiation. Cyclotron radiation, synchrotron radiation, and Bremstallung radiation are all examples of this.

Particles moving through a medium faster than the speed of light in that medium can produce visible kerankov radiation. Certain chemicals produce visible radiation by chemoluminescence. In living things, this process is called bioluminescence. For example, fireflies produce light by this means, and boats moving through water can disturb plankton which produce a glowing weight. Certain substances produce light when they are illuminated by more energetic radiation, a process known as fluorescence. Some substances emit light slowly after exitation by more energetic radiation. This is known as phosphorescence. Phosphorescent material can also be excited by both.

bombarding them with subatomic particles. Cathodal luminescence is one example. This mechanism is used in cathode ray tube television sets and computer monitors. Certain other mechanisms can produce light. Bioluminescence, carincove radiation, electro-luminousens, scintillation, sunilluminescence, tribuluminescence. When the concept of light is intended to include very high energy photons,

gamma rays, Additional generation mechanisms include particle, antiparticle annihilation, radioactive decay. Units and measures Light is measured with two main alternative sets of units. Radiometry consists of measurements of light power at all wavelengths, while photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception. Photometry is usually.

useful, for example, to quantify illumination, lighting, intended for human use. The photometry units are different from most systems of physical units, and that they take into account how the human eye responds to light. The cone cells in the human eye are of three types, which respond differently across the visible spectrum, and the cumulative response peaks at a wavelength of around 555 nanometers. Therefore, two source of light which produce the same intensity of visible light do not necessarily appear equally bright. The photometry units are designed to take this into account, and therefore are a better representation of how bright a light appears to be than raw intensity.

They relate to raw power by a quantity called luminous efficacy, and are used for purposes like determining how to best achieve sufficient illumination for various tasks in indoor and outdoor settings. The illumination measured by a photo cell sensor does not necessarily correspond to what is perceived by the human eye. And without filters, which may be costly, photo cells and charge-coupled devices, CCD, tend to respond to some infrared, ultraviolet, or both. light pressure light exerts physical pressure on objects in its path a phenomenon which can be deduced by Maxwell's equations but can be more easily explained by the particle nature of light

photons strike and transfer their momentum light pressure is equal to the power of the light beam divided by C the speed of light due to the magnitude of C the effect of light pressure is negligible for everyday objects For example, a 1-millimeter exerts a force of about 3.3 piconutons on the object being illuminated. Thus, one could lift a U.S. penny with laser pointers, but doing so would require about 3 billion 1MW laser pointers. However, in nanometer scale applications such as nano-electro-mechanical systems, any MS, the effect of light pressure is more significant.

And exploiting light pressure to drive NEMS mechanisms and to flip nanometer scale physical switches in integrated circuits is an active area of research. At large scale, light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the veins of a windmill. The possibility of making solar sails that would accelerate spaceships in space is also under investigation. Although the motion of the Crooks Radiometer was originally attributed to light pressure, this interpretation is incorrect. A characteristic Crooks rotation is the result of a partial vacuum. It should not be confused with the Nichols Radiometer in which the slight motion caused by torque, though not enough for full rotation against friction, is directly caused by light pressure.

As a consequence of light pressure, Einstein in 1909 predicted the existence of radiation friction, which would oppose the movement of matter. He wrote, radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the motion, front surface, then on the back surface. The backward acting force of pressure exerted on the front surface is thus larger than the force of pressure acting on the back. Hence, as the resultant of the two forces, there remains a force

that counteracts the motion of the plate and that increases with the velocity of the plate. We will call this resultant radiation friction in brief. Usually light momentum is aligned with its direction of motion. However, for example, an evanescent wave's momentum is transverse to direction of propagation. Historical theories about light in chronological order. Classical Greece and Hellenism In the 5th century BC, Empedocles postulated that everything was composed of four elements, fire, air, earth, and water.

He believed that Aphrodite made the human eye out of the four elements, and that she lit the fire in the eye which shone out from the eye, making sight possible. If this were true, then one could see during the night just as well as during the day. So Empedocles postulated an interaction between rays from the eyes and rays from a source such as the sun. In about 300 BC, Euclid wrote Op. Optica in which he studied the properties of light. Euclid postulated that light traveled in straight lines, and he described the laws of reflection and studied them mathematically. He questioned that

sight is the result of a beam from the eye, for he asks how one sees the stars immediately if one closes one's eyes, then opens them at night. If the beam from the eye travels infinitely fast, this is not a problem. In 55 BC, Lucretius, a Roman who carried on the ideas of earlier Greek Adamus, wrote that, the light and heat of the sun, these are composed of minute atoms, which, when they are shoved off, lose no time in shooting right across the inner space of air and the direction imparted by the shove. Despite being similar to later particle theories, Lucretius's views were not generally accepted. Ptolemy, around 2nd century,

wrote about the refraction of light in his book, Optics. Classical India In ancient India, the Hindu schools of Semhaya and Vaishishika from around the early centuries AD developed theories on light. According to the Samhaya School,

light is one of the five fundamental subtle elements, Tamatra, out of which emerge the gross elements. The atomicity of these elements is not specifically mentioned, and it appears that they were actually taken to be continuous. On the other hand, the Vysheeshika school gives an atomic theory of the physical world on the non-atomic ground of ether, space, and time. The basic atoms are those of earth, water, fire, and air. Light rays are taken to be a stream of high velocity of Tejas fire atoms. The particles of light can exhibit different characteristics

depending on the speed and arrangements of the Tejas atoms. The Vishnu Puranah refers to sunlight as the seven rays of the sun. The Indian Buddhists such as Dignica in the 5th century and Darmakirti in the 7th century developed a type of atomism that is a philosophy about reality being composed of atomic entities that are momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy. Descartes. René Descartes held that light was a mechanical property of the luminous body, rejecting the forms of Ibn al-Heitham and Witello,

as well as a species of bacon, crustace, and Kepler. In 1637, he published a theory of the refraction of light that assumed incorrectly, that light traveled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behavior of sound waves. Although Descartes was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave, and in concluding that refraction could be explained by the speed of light in different media. Descartes is not the first to use the mechanical analogies, but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium,

Descartes' theory of light is regarded as the start of modern physical optics. Particle Theory Pierre Gassendi, an atomist proposed a particle theory of light, which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age and preferred his view to Descartes' theory of the plenum. He stated in his hypothesis of light of 1675 that light was composed of corpuscles, particles of manner, which were emitted in all directions from a source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light traveled only in straight lines. He did, however, explain the phenomenon of the diffraction of light,

which had been observed by Francisco Grimaldi, by allowing that a light particle could create a localized wave in the ether. Newton's theory could be used to predict the reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium, because the gravitational pull was greater. Newton published the final version of his theory in the optics of 1704. His reputation helped the particle theory of light to hold sway during the 18th century. The particle theory of light led Laplace to argue that a body could be so massive that light could not escape from it.

In other words, it would become what is now called a black hole. Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light. As has been explained, neither a particle or wave theory is fully correct. A translation of Newton's essay on light appears in the large-scale structure of space-time by Stephen Hawking and George F.R. Ellis. The fact that light could be polarized was for the first time, qualitatively explained by Newton using the particle theory.

Etienne Louis Malou in 1810 created a mathematical particle theory of polarization Jean-Baptiste-Biot in 1812 showed that this theory explained all known phenomena of light polarization At that time, the polarization was considered as the proof of the particle theory wave theory To explain the origin of colors, Robert Hook developed a pulse theory and compared the spreading of light to that of waves and water in his 1665 work, micrographia. In 1672, Hook suggested that light's vibrations could be a perpendicular to the direction of propagation. Christian Huggins worked out in mathematical wave theory of light

in 1678 and published it in his treatise on light in 1690. He proposed the light was emitted in all directions as a series of waves in a medium called luminephorus ether. As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. The wave theory predicted that light waves could interfere with each other like sound waves, as noted around 1800 by Thomas Young. Young showed by means of a different experiment that light behaved as waves. He also proposed that different colors were caused by different wavelengths of light and explained color vision in terms of three color receptors in the eye. Another supporter of the wave theory was Leonhard Euler. He argued in Nova Theoria,

Lucis et Colorum 1746. That diffraction could more easily be explained by a wave theory. In 1816, André Marie Amperi gave us. Augustine Jean Fresnel, an idea that the polarization of light can be explained by the wave theory if light were a transverse wave. Later, Fresnel independently worked out his own wave theory of light, and presented it to the Academia de Science in 1817. Simeon Danny Poisson added to Fresnel's mathematical work to produce a convincing argument in favor of the wave theory, helping to overturn Newton's corpuscular theory.

By the year 1821, Fresno was able to show via mathematical methods that polarization could be explained by the wave theory of light, if and only of light was entirely transverse, with no longitudinal vibration whatsoever. The weakness of the wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance, luminephorus ether, proposed by Huggins in 1678, was cast into the strong doubt in the late 19th century by the Mikkelson-Morley experiment. Newton's corpuscular theory implied that the light would travel faster in a denser medium,

while the wave theory of Huggins and others implied the opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Leon Foucault in 1850. His results supported the wave theory and the classical particle theory was finally abandoned, only to partly re-emerge in the 20th century.